Download Cell Division

Chapter 16
Cellular Reproduction
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Start by completing the Launch Lab on p.549 (take
10 minutes)
Why do cells have to divide?
What is a somatic cell?
To do:
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Complete the 16.1 Review on
p. 555 #1-7
Purpose of Mitosis
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Increase the number of cells (organism
growth)
Repair of damaged cells and replacement
of dead cells
Reproduction for unicellular organisms
Growth, embryonic development, tissue
repair and asexual reproduction involve
mitosis
The 6 “ ”
Words of
Mitosis
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Chromatin
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Chromosomes
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Diffuse nuclear material and forms the
chromosomes present during Interphase
Formed when the chromatin shortens and
condenses (supercoils)
Chromatid
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One of two copies of the replicated
chromosome that are still joined at the
centromere
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Centromere
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Centriole
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A granular body that attaches the two sister
chromatids together
An organelle found in animal cells which organizes
the spindle fibers during nuclear division
Centrosome
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An area of protoplasm that surrounds a pair
of centrioles that are arranged at right
angles to each other
Chromosome
Other
Important
Terms
Mother Cell (Parent cell)
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Original cell that is ready to divide
Daughter Cells
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The two cells resulting from the division
of the mother cell
Have genetically identical nuclei (IB 2.5.5)
Binary Fission
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A form of asexual reproduction where one
cell divides into two equal parts
Ploidy
Number of copies of a set of
chromosomes in a cell
 Haploid -
with only one set of
chromosomes
 Diploid - with two sets of
chromosomes
 Tetraploid - with four sets of
chromosomes
Ploidy
Mother Cell
Diploid
2N
Mother cell
2 copies of 2N
2 x 2N
Daughter Cell
Diploid
2N
Daughter Cell
Diploid
2N
Phases of the Cell Cycle
Interphase Ends
Interphase Begins
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The longest phase of the cell cycle
An active period in the life of a cell when
many metabolic reactions occur, including
protein synthesis, DNA replication, and an
increase in the number of mitochondria
and/or chloroplasts
Regular cell functions
Single stranded chromosomes duplicate
Accumulation of energy supplies
Gap 1 (G1)
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Cell grows and carries out normal
metabolism
Organelles duplicate
Synthesis (S)
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DNA replication
Chromosome duplication
Cell growth
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Cell growth
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Gap 2 (G2)
Second longest phase
 First true phase of cell
division
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Early Prophase
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Centrosome duplicates to form two
centrioles
Centrosome separates and each pair
migrates to opposite poles of the cell (only
in animal cells)
Chromatin threads shorten and become
visible as two sister chromatids joined by a
centromere = supercoiled chromosomes
Late Prophase
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Nuclear membrane dissolves
Nucleolus disappears
Spindle microtubules radiate out at each
pole and extend across the cell
Small fragments of the spindle
microtubules called asters radiate out from
the centriole
Chromosomes
Pair of
Centrioles
What is wrong with
this picture?
Centromere
Aster
Prophase
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Very short phase
Chromosomes are most visible at
this stage
Chromosomes migrate to the
center of the cell (equatorial plate)
Spindle microtubules attach to the
centromeres and the centromeres
divide
Aster
Equatorial
Plate
Spindle Fibers
 Centromeres
divide
 Chromatids move to
opposite poles of the cell
Centrioles
Chromatids
Anaphase
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Opposite of prophase
Centrosome forms in each new cell as the centrioles
duplicate
Chromosomes form a mass through lengthening and
intertwining and diffuse in the nucleoplasm
Cleavage furrow begins to form in animal cells
Nuclear membrane forms around the chromatin
Nucleolus reappears
Spindle microtubules disappear
Cytokinesis
 The
division of cytoplasm
 Provides organelles for
each new cell
 Spindle fibers disappear
Nuclear
Membrane
Cell Cycle in Plant Cells
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Plant cells do not have centrioles and
do not form asters.
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A cell plate forms during telophase in
the centre of the spindle. It becomes
wider to form a new cell wall.
Unique forms of asexual cell
division
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A. Cloning: an identical offspring from
a single cell or mass of cells.
Have been able to grow tissue
transplants from embryonic cells.
Also some simple organisms by
removing the nucleus of an egg cell
then injecting the nucleus from a cell
of a developing embryo.
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Using cells from a fetus or grown
individual does not work. WHY ???
Terms:
enucleated – a cell with its nucleus
removed
totipotent – cell capable of developing
into a new individual
Cancer
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rapid and uncontrolled cell division,
cells do not specialize, capable of
growing in isolation, cells do not
adhere to each other
Can occur in any organ or tissue
Video Clip
 Animation
of Mitosis
 Mitosis Rap
To do:

Complete the 16.2 Review on
p. 561 #1-7
The Formation of Gametes
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Sexual reproduction involves the
union of gametes (sex cells) male:
sperm female: egg or ovum
Gametes have half the number of
chromosomes as a regular cell. They
are said to be haploid (n)
When 2 gametes unite (fertilization),
the resulting zygote will have the
normal number of chromosomes. This
cell is said to be diploid (2n)
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All somatic cells of an organism have
the same number of of chromosomes
except for the gametes. eg. Humans:
46 (somatic cells)
23 (gametes)
Chromosomes occur in pairs that are
similar. These are called homologous
chromosomes.
What is reduction division?
What is recombination?
Meiosis:
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The process of gamete production.
Meiosis happens in 2 stages:
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meiosis l and meiosis ll
Gametes produced have a haploid (n)
number of chromosomes.
(IB 10.1.1)
Stages of Meiosis
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During interphase, the chromosomes
replicate (as they did with mitosis)
then go into meiosis I.
Prophase l:
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Chromosomes form in homologous pairs
- a tetrad forms. (2 pairs of joined
chromatids)
Stages of Meiosis
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- nuclear membrane disappears and
the centrioles move apart.
Crossing Over: Allows for the
exchange of genetic material between
two homologous chromosomes.
Forms a chiasmata in the process (IB
10.1.2)
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Metaphase l:
- Tetrads line up at the cell equator.
- Tetrads attach to the spindle fibers.
Anaphase l :
- Chromatid pairs of each tetrad move
to opposite poles of the cell
(homologous chromosomes separate)
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Telophase l:
- Chromosomes form chromatin
- nuclear membrane forms
- Cytokinesis begins
- The 2 daughter cells have a haploid (n)
chromosome number but they are
doubled called one half of 2n.
Meiosis ll
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Prophase ll: Chromosomes appear,
nuclear membrane disappears, and the
spindle fibers form.
Metaphase ll: Chromatid pairs align at
the equator of the cell.
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Anaphase ll: Centromeres split and the
sister chromatids move to opposite
poles of the cell.
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*Note: The centromeres do not split
during meiosis l.
Telophase ll: Cytokinesis begins,
nuclear membranes form, and
chromosomes form chromatin.
How can meiosis result in virtually
infinite genetic variety in gametes?
1.
2.
Crossing over during prophase 1
Random orientation of homologous
chromosome pairs in metaphase I
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Mendel’s Law of Independent assortment:
(IB 10.1.3 – 10.1.4)
Gametogenesis
The production of mature gametes
from meiotic division.
TWO types:
1.Spermatogenesis: Production of sperm
cells by the male.
 Occurs within the seminiferous tubules
of the male testes.
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2. Oogenesis: The production of the ovum (egg) by
the female.
 Occurs within the follicles of the female ovaries.
 Unequal division of cytoplasm during meiosis l
and ll produces polar bodies. The polar bodies
degenerate and take no part in fertilization.
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Nondisjunction: The unequal
distribution of chromosomes.
2 homologous chromosomes move to
the same pole during meiosis.
A nondisjunction results in one
daughter cell having an extra
chromosome called trisomy and
another daughter cell missing one
called monosomy.
Nondisjunction Disorders in Humans
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Called syndromes – can be seen by
producing a karyotype of the chromosomes
A. Down’s syndrome: 47 chromosomes.
Trisomy 21, may be male or female, risk
factor: 1 in 600, increasing with mothers over
age of 40
Karyotype
Nondisjunction Disorders in Humans
 B. Edward’s syndrome: trisomy of the
18th pair
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C. Patau’s syndrome: trisomy of the 13th
pair
Involving the sex chromosome pair…
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A. Turner’s syndrome: monosomy X –
female with 45 chromosomes
B. Klinefelter’s syndrome: has XXY,
males
C. “Superfemale” syndrome: has trisomy
X or XXX – females
D. “Supermale” syndrome: has XYY
males that are usually criminally insane
What Syndrome would this
be?
What is the difference between
identical and fraternal twins? How is
each formed?
STS issue
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The development of amniocentesis and
chorionic villi sampling (CVS) has
allowed scientists and doctors to get
sample of embryonic cells for
karyotyping.
This allows one to determine genetic
conditions like gender and if a
syndrome is present before birth.
How may this be used???????????
Comparing Mitosis and Meiosis
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1. Number of divisions
Mitosis
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2. Number of daughter cells
produced.
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3. Number of chromosomes
in mother cell.
Meiosis
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4. Number of chromosomes
in daughter cells.
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5. Body (somatic) cells produced.
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6. Gametes produced.
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7. Genetic content of daughter
cells compared to mother cell
To do:

Complete the 16.3 Review on
p. 572 #1-10
Reproduction Strategies
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Using your textbook (p.573-580)
complete the following information
with definitions and examples.
Type of Asexual Reproduction
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1. Budding:
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2. Vegetative reproduction:
Type of Asexual Reproduction
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3. Fragmentation:
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4. Parthenogenesis:
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5. Spores:
Alternation of Generations
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What is it?
also called Metagenesis, or Heterogenesis,
alternation of a sexual phase and an asexual phase in
the life cycle of an organism.
The two phases, or generations, are often
morphologically, and sometimes chromosomally,
distinct.
Examples of organisms that use it:
Alternation of Generations
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What is a sporophyte?
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What is a gametophyte?
Explain the following diagram:
Animation
Explain the following diagram:
To do:
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Do Thought Lab 16.2 on p.579
Do Section 16.4 Review on p. 580 #1-9